The present study is designed to test the hypothesis that fetal splanchnic nerves are necessary for normal physiological fetal adrenocortical function in response to acute and chronic hypoxemia. This hypothesis will be tested utilizing fetal sheep with splanchnic nerve ablation and it is anticipated that adrenocortical responses will be blunted after splanchnic nerve section. Selected vascular, hormonal, cellular, and molecular responses of the fetal adrenal and sympathetic spinal cord will be quantified in response to an acute 60 minute (Aim 1) or a chronic 24 hour (Aim 2) hypoxemic challenge induced by infusion of nitrogen into the maternal trachea. Hormonal endpoints will be fetal cortisol, ACTH, AVP, PGE2, catecholamines, and maternal cortisol plasma concentrations. Molecular determinations will include immunocytochemical staining, in situ hybridization, and Northern and Western analysis of steroidogenic enzymes, CRH, c-fos, c-jun, PNMT, tyrosine hydroxylase, and glucocorticoid receptors in the fetal adrenal and sympathetic spinal cord.